Generally, the transport of containers, for example, can bodies or open-end cans is carried out with conveyers, for example, to bring the cans to a treatment zone. Such conveyers are also used to move the containers successively through the treatment zone or zones in a predetermined processing sequence.
It is also customary that the containers are disposed upstandingly and in closely spaced sequence on the respective conveyer, but often without lateral supports for the containers. At best, lateral guide bars or rails are provided to preclude lateral displacement on and falling of the containers from the conveyer. The lateral guides are either included in the conveyer or extend as locally fixed bars laterally along the conveyer. For example, the containers are brought to drying or heat treating furnaces, Such as annealing or similar furnaces, as well as being passed through such furnaces. The containers are then carried to other locations or zones provided along the path of the conveyer, or conveyers, until their processing is completed.
Often vacuum-type conveyers are used for the transport of such containers with the cans standing on the conveyer and with open ends directed towards the conveyer. Vacuum or suction is applied at the open end of a container and the can is held in this manner for transport by the conveyer. These systems are characterized by considerable difficulties in producing and sustaining vacuum conditions in the containers or cans which are disposed with their open ends on the conveyer.
There are also known magnetic conveyers which transport cans having one open end and made of a ferromagnetic material. These conveyers securely retain the containers by magnetic forces.
The proper retention of the containers presents problems in known systems, especially when the direction of travel is changed during the course of travel of the conveyer. For example, the direction of travel may change by 90.degree. from the horizontal into the vertical or upward direction or downward direction. Problems can arise because the suction force of the vacuum conveyer, or the magnetic attraction of magnetic conveyers, respectively, can only be effectively applied with full contact of the container on the conveyer.
These particular holding/retention means for producing and maintaining a secure standing of the cans on the known conveyers are not entirely useful for operations calling for full immersion of the conveyed items. They also have only limited applicability in treatment steps in which all sides of the containers will be subjected to the action of a treating medium, during drying, baking, or burning-in of a coating and, at best, can carry out these steps only with considerable disadvantage.
Thus, special holding devices have been developed for treating fully immersed can bodies. The holding devices are arranged above the immersion bath and are comprised of two sieve-like carriers which extend parallel with respect to one another and which are generally planar. The can bodies are held between these carriers and are lowered together with the carriers into the fluid.
The dipping or immersion treatment of can bodies which have one open end cannot be successfully carried out with such cooperating sieve carriers. Instead, rotating tables with immersion cells have been developed for such applications, for example, electro-immersion painting or electrocoating. In these, the container bodies are introduced so that their open ends are downwardly directed as well as being centered and held by an electrode which attaches at the center point on the outer side or surface of the container bottom of the can. A special introduction and removal system for the electrolyte is provided, and the container is surrounded on all sides by the electrolyte (European OS No. 0019669).